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   1 // Tencent is pleased to support the open source community by making RapidJSON available.
   2 //
   3 // Copyright (C) 2015 THL A29 Limited, a Tencent company, and Milo Yip. All rights reserved.
   4 //
   5 // Licensed under the MIT License (the "License"); you may not use this file except
   6 // in compliance with the License. You may obtain a copy of the License at
   7 //
   8 // http://opensource.org/licenses/MIT
   9 //
  10 // Unless required by applicable law or agreed to in writing, software distributed
  11 // under the License is distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR
  12 // CONDITIONS OF ANY KIND, either express or implied. See the License for the
  13 // specific language governing permissions and limitations under the License.
  14
  15 #ifndef RAPIDJSON_ISTREAMWRAPPER_H_
  16 #define RAPIDJSON_ISTREAMWRAPPER_H_
  17
  18 #include "stream.h"
  19 #include <iosfwd>
  20 #include <ios>
  21
  22 #ifdef __clang__
  23 RAPIDJSON_DIAG_PUSH
  24 RAPIDJSON_DIAG_OFF(padded)
  25 #elif defined(_MSC_VER)
  26 RAPIDJSON_DIAG_PUSH
  27 RAPIDJSON_DIAG_OFF(4351) // new behavior: elements of array 'array' will be default initialized
  28 #endif
  29
  30 RAPIDJSON_NAMESPACE_BEGIN
  31
  32 //! Wrapper of \c std::basic_istream into RapidJSON's Stream concept.
  33 /*!
  34     The classes can be wrapped including but not limited to:
  35
  36     - \c std::istringstream
  37     - \c std::stringstream
  38     - \c std::wistringstream
  39     - \c std::wstringstream
  40     - \c std::ifstream
  41     - \c std::fstream
  42     - \c std::wifstream
  43     - \c std::wfstream
  44
  45     \tparam StreamType Class derived from \c std::basic_istream.
  46 */
  47
  48 template <typename StreamType>
  49 class BasicIStreamWrapper {
  50 public:
  51     typedef typename StreamType::char_type Ch;
  52
  53     //! Constructor.
  54     /*!
  55         \param stream stream opened for read.
  56     */
  57     BasicIStreamWrapper(StreamType &stream) : stream_(stream), buffer_(peekBuffer_), bufferSize_(4), bufferLast_(0), current_(buffer_), readCount_(0), count_(0), eof_(false) {
  58         Read();
  59     }
  60
  61     //! Constructor.
  62     /*!
  63         \param stream stream opened for read.
  64         \param buffer user-supplied buffer.
  65         \param bufferSize size of buffer in bytes. Must >=4 bytes.
  66     */
  67     BasicIStreamWrapper(StreamType &stream, char* buffer, size_t bufferSize) : stream_(stream), buffer_(buffer), bufferSize_(bufferSize), bufferLast_(0), current_(buffer_), readCount_(0), count_(0), eof_(false) {
  68         RAPIDJSON_ASSERT(bufferSize >= 4);
  69         Read();
  70     }
  71
  72     Ch Peek() const { return *current_; }
  73     Ch Take() { Ch c = *current_; Read(); return c; }
  74     size_t Tell() const { return count_ + static_cast<size_t>(current_ - buffer_); }
  75
  76     // Not implemented
  77     void Put(Ch) { RAPIDJSON_ASSERT(false); }
  78     void Flush() { RAPIDJSON_ASSERT(false); }
  79     Ch* PutBegin() { RAPIDJSON_ASSERT(false); return 0; }
  80     size_t PutEnd(Ch*) { RAPIDJSON_ASSERT(false); return 0; }
  81
  82     // For encoding detection only.
  83     const Ch* Peek4() const {
  84         return (current_ + 4 - !eof_ <= bufferLast_) ? current_ : 0;
  85     }
  86
  87 private:
  88     BasicIStreamWrapper();
  89     BasicIStreamWrapper(const BasicIStreamWrapper&);
  90     BasicIStreamWrapper& operator=(const BasicIStreamWrapper&);
  91
  92     void Read() {
  93         if (current_ < bufferLast_)
  94             ++current_;
  95         else if (!eof_) {
  96             count_ += readCount_;
  97             readCount_ = bufferSize_;
  98             bufferLast_ = buffer_ + readCount_ - 1;
  99             current_ = buffer_;
 100
 101             if (!stream_.read(buffer_, static_cast<std::streamsize>(bufferSize_))) {
 102                 readCount_ = static_cast<size_t>(stream_.gcount());
 103                 *(bufferLast_ = buffer_ + readCount_) = '\0';
 104                 eof_ = true;
 105             }
 106         }
 107     }
 108
 109     StreamType &stream_;
 110     Ch peekBuffer_[4], *buffer_;
 111     size_t bufferSize_;
 112     Ch *bufferLast_;
 113     Ch *current_;
 114     size_t readCount_;
 115     size_t count_;  //!< Number of characters read
 116     bool eof_;
 117 };
 118
 119 typedef BasicIStreamWrapper<std::istream> IStreamWrapper;
 120 typedef BasicIStreamWrapper<std::wistream> WIStreamWrapper;
 121
 122 #if defined(__clang__) || defined(_MSC_VER)
 123 RAPIDJSON_DIAG_POP
 124 #endif
 125
 126 RAPIDJSON_NAMESPACE_END
 127
 128 #endif // RAPIDJSON_ISTREAMWRAPPER_H_